‘Air-breathing’ battery could cut costs of renewable energy storage.

Technology: Wind and solar power are increasingly popular sources for renewable energy. But intermittency issues keep them from connecting widely in the world. They require energy-storage systems that, at the cheapest, run about $100 per kilowatt hour and function only in certain locations. MIT researchers have developed an “air-breathing” battery that could store electricity for very long durations for about one-fifth the cost of current technologies, with minimal location restraints and zero emissions. The battery could be used to make sporadic renewable power a more reliable source of electricity for the grid.

The rechargeable flow battery uses cheap, abundant sulphur dissolved in water. An aerated liquid salt solution in the cathode continuously takes in and releases oxygen that balances charge as ions shuttle between the electrodes. Oxygen flowing into the cathode causes the anode to discharge electrons to an external circuit. Oxygen flowing out sends electrons back to the anode, recharging the battery. The battery’s total chemical cost—the combined price of the cathode, anode, and electrolyte materials—is about 1/30th the cost of competing batteries, such as lithium-ion batteries. Scaled-up systems could be used to store electricity from wind or solar power, for multiple days to entire seasons, for about $20 to $30 per kilowatt hour.

It is a type of flow battery, where electrolytes are continuously pumped through electrodes and travel through a reaction cell to create charge or discharge. The battery consists of a liquid anode (anolyte) of polysulfide that contains lithium or sodium ions, and a liquid cathode (catholyte) that consists of an oxygenated dissolved salt, separated by a membrane. Upon discharging, the anolyte releases electrons into an external circuit and the lithium or sodium ions travel to the cathode. At the same time, to maintain electroneutrality, the catholyte draws in oxygen, creating negatively charged hydroxide ions. When charging, the process is simply reversed. Oxygen is expelled from the catholyte, increasing hydrogen ions, which donate electrons back to the anolyte through the external circuit. This battery literally inhales and exhales air, but it doesn’t exhale carbon dioxide, like humans—it exhales oxygen.

Because the battery uses ultra-low-cost materials, its chemical cost is one of the lowest—if not the lowest—of any rechargeable battery to enable cost-effective long-duration discharge. Its energy density is slightly lower than today’s lithium-ion batteries.

Stake Holders:

Manufacturing units

Energy Manager

Commercial building users

Utility Company

Engineer

Deployment / Implementation:

Step one: Showcase the reliability of the technology to the public and private entities. Attract more investors and spread awareness about the usage to this technology.

Step two: Set up some full-scale prototype units to prove the principles in real-world conditions.

Step three: Form partnership with utility companies (Solar and wind energy) that could use this technology in their buildings to demonstrate the efficiency of the technology.

I think fog harvesting can be proven as a sustainable and scalable solution to water scarcity. But my only worry is about the reliability of the water source for these fog harvesting technologies, because occurrence of fog is very much uncertain. Further, calculation of even an approximate quantity of water that can be obtained at a particular location is difficult. The technology might represent an investment risk unless a pilot project is first carried out to quantify the potential water rate yield that can be anticipated in the area under consideration.